That would be a "surge protector". Note that many UPS (uninterruptable power supply) units include this functionality too.
See related links. This company specialized in patented lightning isolation devices to protect your electrical equipment from lightning surges.
It is a device used on power systems above 1000 volts to protect other equipment from lightning and switching surges.
It's true that a surge protector would protect against surges like those caused by lightning strikes but would do nothing to help with sags and brownouts. To address both high voltage (surges) and low voltage (brownouts) you would need an uninterruptible power supply (UPS). A UPS provides clean current by powering your computer from the battery while simultaneously charging the battery from the electrical supply.
how can starta surfwear protect there system against power surges
Short circuits.
The best protection is a good UPS (Uninterruptible Power Supply). That will protect you against both surges and brown outs, as well as allowing you to power down safely in case of a power outage.
it cant protect the system against power surges
Ground your self with a rest band or standing ona floor mate.
An AVR is an automatic voltage regulator. It is a device that intercepts fluctuations in the power supplied to the computer and ensures that neither power surges or brownouts affect it.
Provides protection during mains power surges and lightning strikes.
a sertain way
Yes it can. In fact, if your computer and modem are both plugged into an UPS you may be able to continue surfing during a power outage. It will also protect the modem from power line surges and brown outs that could otherwise be destructive. Many UPS have jacks to plug the telephone line in to protect against surges on the telephone line (phone modems) but typically don't have protection for surges on cable.